The use of molding compositions, both sheet and bulk, is well known. Generally such molding compositions comprise a thermoplastic polyester resin and various fillers and reinforcements in combination with a crosslinking agent. However, various thermoplastic polyester resins as polyethylene terephthalate (PET), (1,4-polybutylene terephthalate) (PBT), poly(1,4-chclohexane dimethanol terephthalate) (PCT) mixtures thereof and the like have not previously been found to be especially suitable for use as molding resins due to their brittleness when molded in thick sections. The resulting molding compositions often lack the desired physical strength characteristics.
It is customary to incorporate into the molding compounds various fillers and reinforcements which provide bulk and strength. Principal among such reinforcements are glass fibers which generally have diameters of about 0.0025 to 0.0075 inch and lengths of about 0.13 to about 2.00 inch. In order to facilitate the handling of the glass fibers, it is customary that they be sized immediately upon forming. It is advantageous if the size composition serves not only to facilitate the handling of the glass fibers but also if the size acts to create a bond between the glass fibers and the resin such that the strength properties of the molded resin are improved. The glass size composition of this invention possesses such properties.